A terrorist attack just before the American presidential polls in November could result in a win for Republican candidate Donald Trump, said an expert on the Middle East.

And this would suit a terrorist organisation such as the Islamic State in Iraq and Syria (ISIS), said Dr Nader Hashemi of the University of Denver, The Star reported.

"The big fear in the US now is if in October, one month before the presidential election, you have a major terrorist attack similar to Orlando or Paris - that is enough to put Donald Trump in the White House," he said at a seminar recently.

A shooting at a gay nightclub in Orlando by an American-born man who had pledged allegiance to ISIS resulted in 49 people being killed and 52 others injured. It was the deadliest mass shooting in the US.

Last December, Mr Trump had called for a ban on all Muslims from entering the US until it could figure out what's going on.

But since he was elected Republican nominee for the presidential race, Mr Trump has called for a ban on anyone immigrating to the country from areas of the world that have a history of terrorism against America or its allies.